This invention relates generally to shaft sealing devices for use with rotating equipment. Adequate maintenance of rotating equipment is difficult to obtain because of extreme equipment duty cycles, the lessening of service factors, design and the lack of spare rotating equipment in many processing plants. This is especially true of machine tool spindles, wet end paper machine rolls, aluminum rolling mills and steam quench pumps and other equipment utilizing extreme contamination affecting lubrication.
Various forms of shaft sealing devices have been utilized to try to protect the integrity of the bearing environment, including rubber lip seals, clearance labyrinth seals, and attraction magnetic seals. Lip seals or O-ring shaft seals can quickly wear out and fail and are also known to permit excessive amounts of moisture and other contaminants to immigrate into oil reservoir of the operating equipment even before failure had the interface between the rotor and the stator exposed to the contaminates or lubricants at the radial extremity of the seal.
Labyrinth-type seals involving closely related stator and rotor rings, which do not contact each other but define labyrinth passages between them have been devised and utilized and are illustrated in Orlowski, U.S. Pat. Nos. 4,706,968; 4,989,883; 5,069,461; and the additional patents to Orlowski cited therein. As described in Orlowski U.S. Pat. Nos. 4,989,883 and 5,069,461, improvements in labyrinth seals are disclosed including the utilization of various forms of O-ring seals to improve the static sealing action when the shaft is at rest and non-contact dynamic sealing action is provided when the shaft is rotating.
An improvement over these labyrinth seals and o-ring seals is described in U.S. Pat. No. 5,378,000. There the isolator or seal provides a sealing ring inserted in recesses in the rotor and the stator to lock together the rotor and stator in an axial direction. This actual lock up of rotor and stator dramatically reduces the possibility of migration of rotor from stator. The resultant is a reduced radial interface gap variation from that which had existed previously between the rotor and the stator.
An objective of the present invention is to provide an improvement to seals or bearing isolators to prevent leakage of lubricant and entry of contaminants by encompassing the stator within the rotor to create an axial directed interface at the radial extremity of the rotor. Prior art seals traditionally had the interface between the rotor and the stator exposed radially to the contaminants or lubricants at the radial extremity of the seal.
The projection of an axial portion of the stator into the rotor has been expanded radially. This projection or protruding member of the stator into the rotor has been expanded radially beyond the diameter of the major portion or body of the stator.
The rotor and the resultant recess 22 in the stator, which previously surrounded the stator projection or insertion, is also extended radially beyond the major portion of the stator. The rotor now encompasses the stator, or a substantial portion of the stator radial projection, in such a manner that the interface presented to the ingress of the lubricant or contaminates is facing axially and rearwardly. The axial facing interface presents a limited access to the internal of the seal and a constant dimensional interface between the rotor and the stator regardless of any axial movement of the rotor with respect to the stator.
A groove 23 may be machined into the stator to accentuate the novel radial extension of the rotor and the stator. This groove improves the ability of the seal to prevent contaminates from entering the axial interface gap between the rotor and the stator.
This novel improvement i.e. the encapsulation of the radial extension stator by the rotor enables the interface gap between the accessible portions of the stator and the rotor to be of a predetermined dimension. The improvement also means that there is no fluctuation or variation in the interface gap resulting from any relative axial movement between the rotor and the stator.
This novel seal or bearing isolator will operate to vastly improve the rejection or ingress of contaminants into the interface gap between the rotor and stator. The entrance to the interface gap is facing or directed away from the normal flow of contaminants i.e. along the axis of the shaft toward the housing. The interface gap can be machined to extremely close tolerances because there is no movement radially between the rotor and the stator and any axial movement does not affect the interface.
Other objects, advantages embodiments of the invention will become apparent upon the reading the following detailed description and upon reference to drawings and the prior art patents.